Electrical condenser



May 4, 1943. J. A. FLANZER ETAL 2,318,070

ELECTRI CAL CGNDENSER Filed Nov. 8, 1940 e2 MMF INVENTORS JOSEPH A.FLANZER PHILIP BEIN Y 9 W M ATTORNEYS Patented May 4, 1943 UNlTED STATESPATENT OFFlCn ELECTRICAL CONDENSER Application November 8, 1945), SerialNo. 364,856

10 Claims.

This invention relates to electrical condensers, and more particularlyto trimmer condensers such as are employed for push-button tuning ofradio receivers.

The primary object of the present invention is to generally improvetrimmer condensers of the specified character.

For broadcast station selection, it has been customary to provide a gangof trimmer condensers which are used in conjunction with a suitableswitching arrangement controlled by push-buttons. Each trimmer condenseris adjustable by means of a suitable adjusting screw, therebydetermining the station selected by its associated push-button. However,the widest range of any single commercially available trimmer condenserhas not been large enough to permit the selection of a station anywherein the broadcast frequency band. Thus, smaller condensers have been usedfor stations at one end of the band, and larger condensers for stationsat the other end of the band. In practice, the gang of trimmercondensers would ordinarily have a progressive number of condenserplates, including three, four and five-plate condensers. As a. result,it has been necessary for the owner of the radio receiver to tune thepush-buttons in the order of progressive broadcast frequencies, and toselect stations reasonably well spread over the broadcast frequencyband.

One primary object of the present invention is to overcome the foregoinglimitations. For low cost and convenience, it is desirable that this bedone while using only a single capacitor unit requiring only a singlemounting and a single set of connecting wires, and devoid of a switch orthe like for adding or subtracting the extra capacitance. Our object,therefore, is to provide a single inexpensive trimmer condenser havingso large a range of adjustment as to be useable for tuning throughoutthe broadcast frequency band. The condensers in a gang of condensers maythen be all alike, and any button may be set for the selection of anystation in the broadcast band.

To the accomplishment of the foregoing, and other more particularizedobiects which will hereinafter appear, our invention consists in theelectrical condenser elements and their relation one to the other, ashereinafter are more particularly described in the specification, andsou ht to be defined in the claims. The specification is accompanied bya drawing, in which:

Fig. 1 is a longitudinal section through a condenser embodying featuresof our invention;

Fig. 2 is a. top plan view thereof;

Fig. 3 is a bottom plan View thereof;

Fig. 4 is a schematic diagram showing the metal condenser plates alone;

Fig. 5 is a graph explanatory of the operation and advantage of theimproved condenser; and

Fig. 6 illustrates the manner in which the con denser may be mounted ingang formation.

So far as We are aware, no previously available trimmer condenser can beused with a pushbutton switch arrangement so as to cover the entirebroadcast band, by means of a single adjusting screw. For example, ananalysis of the capacitance range of a Well-known line of trimmercondensers reveals that the two-plate condensers of this particularmanufacturer has a maximum capacitance of 100 mmf., and a minimumcapacitance of 4 mmf. The three-plate trimmer has a maximum capacitanceof 230 mmf. and a minimum capacitance of 6 mmf. The four-plate condenserhas a maximum capacitance of 350 mmf. and a minimum capacitance of 20mmf. The five-plate condenser has a maximum capacitance of 500 mmf. anda minimum capacitance of 35 mmf. On computing the ratio of maximum tominimum capacitance for each of these condensers, we find that the ratiofor the two-plate condenser is 25 to 1; the ratio for the three-platecondenser is 35 to l; the ratio for the four-plate condenser is about 17to 1; and the ratio for the five-plate condenser is about 15 to 1. Thusthe greatest ratio between maxi mum and minimum capacitance is obtainedin the case of the three-plate condenser.

But, while the ratio of maximum to minimum capacitance is large, theactual maximum capacitance is relatively small. However, by connectingtwo of these three-plate condensers in parallel, the maximum capacitancemay be doubled to 460 mmf., and by so arranging the two con-- densers asto be adjusted by means of a single screw, the range of variationextends from 13 to 460 mmf.

More generally, the underlying concept of the present invention is toemploy a plurality, ordinarily two, trimmer condensers, which have alarge ratio of maximum to minimum capacitance, while having only arelatively small maximum capacitance, and then by connecting thetrimmers in parallel and embodying the same in a structure such thatthey may be simultaneously varied by a single adjusting means, theresulting trimmer will be characterized by relatively large maximumcapacitance and a large ratio of maximum to minimum capacitance, thusproviding the desired large range of capacitance variation.

In the specific case discussed above, the range of our improved trimmercondenser is from 13 to 460 mmf. It is true that this is not as large arange as has heretofore been provided. It has been customary for setmanufacturers to use the three, four and five-plate trimmers, thusproviding a capacitance range of from 6 /2 to 500 mmf. However, oninvestigation, we find that this has been done largely because the extrarange was anyway inherently available in the commercial trimmers whichwere required for push-button tuning. The broadcast band has a frequencyratio of approximately 3 /2 to 1. The capacitance needed for thispurpose varies as the square of the frequency, and therefore thecapacitance ratio would have to be 12% to 1. Assuming that the rest ofthe circuit being tuned has distributed capacitance of 20 mmf., thisfigure added to, say, 15 mmf. as a working minimum for the trimmercondenser, would give a total minimum of 35 mmf. The maximum thereforewould have to be about 430 mmf. Obviously, a trimmer having a workingrange of 15 to 430 mmf. should prove entirely satisfactory. This workingrange will be safely covered by the trimmer condenser disclosed hereinwith its range of 13 to 460 mmf., the maximum preferably being somewhatexcessive because the capacitance values obtained near the fully tightposition of the adjusting screw, are too critical in adjustment, andtherefore not conveniently useable.

Referring now to the drawing, and more particularly to Figs. 1, 2 and 3,our improved trimmer condenser comprises a first trimmer condensergenerally designated l2, and a second, generally designated l4, thesebeing connected electrically in parallel by means of the tubular memberl6 and screw 18, at one side of the condensers, and by means of aflexible, multiple-strand wire 20 at the other side of the condensers.One of the condensers is provided with an internally threaded bushing22, and a single adjusting screw 24 passes through both condensers andbushing 22. As is usual with these condensers, the plates tend normallyto open or spread apart, and tightening of screw 24 tends to close orbring the same together, thereby increasing th capacitance. It will beevident that the single screw functions to simultaneously increase ordecrease the capacitance of both of the component trimmer condensers.

Considering the arrangement in greater detail, each of the condensershere employed is a threeplate condenser, and may be constructed partlyalong lines such as those set forth in Flanzer Patent No. 2,209,546,issued July 30, 1940, and entitled Condenser. Specifically, thecondenser I2 comprises a suitable insulation base 26 which may be madeof a molded ceramic. The bottom plate 28 is a fiat plate restingdirectly on the top surface of base 26, and is eyeletted thereto at oneend of the base by means of the eyelet 31!. A mica film 32 is disposedabove plate 28, and is also held in position by the eyelet 30. Theintermediate plate 34 is a curved plate which is secured at the oppositeend of base 26 by means of an eyelet 36. A mica film 38 is disposedabove plate 34, and is also held in position by the eyelet 36. The topplate 49 is made of heavier gauge metal, and is bent upwardly at 42,downwardly at 44, and inwardly beneath the base of the condenser at 46,where it is secured to the base by the eyelet 30 previously referred to.The center part of the "plate is cut away at 42 and 44, thus leaving twospaced arms Which increase the yieldability of the movable plate 40.Some of the waste metal struck from between the spaced arms may be bentoutwardly, as is indicated at 48, thus forming a means for bothelectrical and mechanical connection to the condenser l 4. A contactstrip 50 may be bent outwardly above the support 48 to insure connectionto the bottom plate 28 as well as the top plate 40. The actual wireconnection may be made to a suitable soldering lug 52 projectingsidewardly from the condenser. 7

At the opposite side of the condenser the interme-diate plate 34 may beextended outwardly, as indicated at 54, to provide a soldering lug, andinasmuch as the metal of the intermediate plate is quite thin, thisextension 54 is preferably backed by a support piece 56 made of thickermetal and secured in position by the eyelet 36 previously referred to.

The upper condenser I4 is somewhat similar to the lower condenser l2,but is preferably disposed in inverted position, that is, the condensersI2 and I4 are preferably arranged face to face. The outsideconfiguration of the ceramic base 60 may be similar to that of the base26. A flat metal plate 62 rests against base 60, and is eyelettedthereto, together with a mica dielectric insulation film 64, by means ofeyelet 66. A curved intermediate plate 68 is secured to the opposite endof base 60 by means of an eyelet Ill, and this eyelet preferably alsoholds a mica dielectric film 12. The outer plate 14 is a thick platebent and secured in position much as was described in connection withthe plate 49, the inwardly bent part 16 of plate 14 being fastened byeyelet 66.

The extension 13 of fiat plate 62 and the extension of late 14 are heldtogether and are spaced from the extensions 48 and 53 of condenser i2 bymeans 'of tubular spacer 16, the assembly being held together by screwl8 and nut 82. The extensions 18 and 80 are sufficiently flexible topermit movement or change in angularity of the base 60 relative to thebase 23. For this purpose, the extension 80 may be weakened or necked,as indicated at 81 in Fig. 2.

Conductor 20 extends from the middle or intermediate plate 68 ofcondenser l4, to the intermediate plate 34 of condenser l2. Thus thecondensers are connected electrically in parallel, and the only externalconnections needed are to the soldering lugs 52 and 54.

The insulation base 26 of condenser 12 is provided with the threadedbushing 22 previously referred to, but the base 60 of condenser I4 hasno such bushing, and instead, the adjusting screw 24 passes withconsiderable clearance through base Bi! and the upper and lowercondenser plates. A pair of washers B4 are preferably disposed betweenthe outer plates 40 and 14 of the condenser, and these washerspreferably have arcuate surfaces where they contact one another, andfiat surfaces where they contact the condenser plates, thus helpingcompensate for angularity as the condenser adjustment is changed.

It will be understood that the disposition of a single curved condenserplate between two relatively flat condenser plates, one of which seeksnormally to open to an angular position relative to the other, helpsproduce a maximum opening of the condensers, and therefore the desired.largge ratio of maiximum-to-minimum capacitance. This will be clearfrom consideration of Fig. 4, which schematically illustrates the metalcondenser plates alone, the lower condenser comprising a curved plate 34between flat plates 28 and 40, and the upper condenser comprising acurved plate 68 between flat plates 62 and 14.

The condenser may be mounted in any desired manner which will afiordrelative movement of the condensers during adjustment of the same. Wefind it convenient to treat one of the condensers as a stationarycondenser, so that the desired relative movement takes place inconnection with the other condenser. Specifically, the lower condenserI2 is here treated as a stationary condenser, and it is preferablyprovided with a staple-like mounting 86, the flat or bridge portion ofwhich is secured to the bottom of ceramic base 26 by means of thebushing 22 previously referred to. The staple is provided with spaceddownwardly bent legs 88 which may subsequently be bent when securing thecondenser to a mounting strip. A gang or bank of condensers may bemounted side by side on a single mounting strip, and this is indicatedin Fig. 6, showing a fragmentary portion of a mounting strip 90 on whichcondensers 92, 94 and 96 are secured by means of staple mountings 86(Fig. 3). The strip 90 (Fig. 6) is provided with holes 98 for thebushing and adjusting screw, and with associated pairs of holes I00 forthe staple legs 88, the latter being passed through the holes I00 andbent over or clinched.

as indicated in the drawing. The soldering lugs 52 and 55 of thecondensers project sidewardly from the strip 991 and are accessible forwiring. Figure 6 is, of course, a bottom plan view, and shows the gangin inverted position.

The construction and operation, as well as the advantages of ourimproved trimmer condenser, will be apparent from the foregoing detaileddescription thereof. The operating advantage of the condenser may befurther illustrated by reference to the graph shown in Fig. 5, in whichthe dotted line I02 represents the capacitance characteristic of afive-plate trimmer condenser, while the solid line curve I04 representsthe capacitance characteristic of our new trimmer condenser. It will beobserved that whereas the capacitance of the five-plate condenser levelsoff at a relatively high value of about 35 or 40 mmf., the capacitanceof the special twin three-plate condenser of our invention diminishes toa very much lower value of,

say, 13 mmf. The capacitance has been represented on a logarithmic scalebecause of the importance of showing the results at the low end of thescale.

It will be understood that while we have referred to quantitativecapacitance values at various points in the foregoing description, thesevalues have been given solely by way of exemplification and not inlimitation of the invention.

It will be apparent that while we have shown and described our inventionin a preferred form, many changes and modifications may be made in thestructure disclosed, without departing from the spirit of the inventionas sought to be defined in the following claims.

We claim:

1. A wide-range trimmer condenser comprising two trimmer condensersarranged one above the other in face to face or inverted relation, eachof said condensers comprising an insulation base having a plurality ofnormally openable metallic plates, the lower base being provided with aninternally threaded bushing and having a mounting staple secured to thebottom of the base by said bushing, a single adjusting screw passingthrough the upper base and the plates of the upper and lower condensers,to the threaded bushing, whereby rotation of said screw simultaneouslyadjusts both condensers, means movably mounting the upper base formovement relative to the lower base, and means connecting saidcondensers in parallel.

2. A wide-range trimmer condenser comprising two trimmer condensersarranged one above the other in face to face or inverted relation, eachof said condensers comprising an insulation base having a plurality ofnormally openable metallic plates with mica film dielectric insulationtherebetween, alternate plates being eyeletted at opposite ends of thebase, the lower base being provided with an internally threaded bushingand having a mounting staple secured to the bottom of the base by saidbushing, a single adjusting screw passing through the upper base and theplates of the upper and lower condensers to the threaded bushing,whereby rotation of said screw simultaneously adjusts both condensers,means movably mounting the upper base for movement relative to the lowerbase, and means connecting said condensers in parallel,

3. A wide-range trimmer condenser comprising two trimmer condensersarranged one above the other in face to face or inverted relation, eachor said condensers having a comparatively small capacitance but a largeratio of maximum-tominimum capacitance, each of said condenserscomprising an insulation base having a plurality of normally openablemetallic plates with mica film dielectric insulation therebetween,alternate piaies bein. eyeletted at opposite ends of the base, the lowerbase being provided with an internally threaded bushing and having amounting staple secured to the bottom of the base by said bushing, asingle adjusting screw passing through the upper base and the plates ofthe upper and lower condensers and the threaded bushing, wherebyrotation of said screw simultaneously adjusts both condensers, meansmovably mounting the upper base for movement rela tive to the lowerbase, and means connecting said condensers in parallel, therebyproviding a con denser of relatively large capacitance and a high ratioof maximum-to-minimun: capacitance.

4. A wide-range trimmer condenser comprising two trimmer condensersarranged one above the other in face to face or inverted relation, eachof said condensers being a three-plate condenser having an insulationbase, the lower base being provided with an internally threaded bushing,a single adjusting screw passing through the upper base and the platesof the upper and lower condensers to the threaded bushing, wherebyrotation of said screw simultaneously increases or decreases thecapacitance of both condensers, means movably mounting the upper basefor movement relative to the lower base, and means connecting saidcondensers in parallel.

5. A wide-range trimmer condenser comprising two trimmer condensersarranged one above the other in face to face or inverted relation, eachof said condensers being a three-plate condenser having an insulationbase, a flat bottom plate adjacent the base, a curved intermediateplate, a resilient normally open outer plate, and insulation mica filmsbetween said plates, alternate plates being eyeletted at opposite endsof the base, the lower base being provided with an internally threadedbushing and having a mounting staple secured to the bottom of the baseby said' bushing, a single adjusting screw passing through the upperbase and the plates of the upper and lower condensers and the threadedbushing, whereby rotation of said screw simultaneously increases ordecreases the capacitance ofv both condensers, means movably mountingthe upper base for movement relative to the lower base, and meansconnecting said condensers in parallel.

, 6. A single wide-range trimmer condenser comp-rising two trimmercondensers coupled together and arranged one above the other, each ofsaid trimmer condensers having its own insulation base with a set ofcondenser plates attached thereto, means connecting said trimmercondensers in parallel, one of said condenser bases having a threadedpart, and a single adjusting screw mating with said threaded part andpassing through the condenser plates of both condensers and through thebase of the other condenser and bearing against a part of said othercondenser, whereby rotation of said screw operates to move one condenserrelatively to the other and to move the plates of both condensers tosimultaneously increase or decrease the capacitance of both condensers.

'7. A single wide-range trimmer condenser comprising two trimmercondensers coupled together and arranged one above the other, each ofsaid trimmer condensers having its own insulation base with a set ofcondenser plates attached thereto, each said set consisting of a, bottom plate adjacent the base, an intermediate plate, and a top plate,meansconnecting said trimmer condensers in parallel, one of saidcondenser bases having a threaded part, and a single adjusting screwmating with said threaded part and passing through the condenser platesof both condensers and through the base of the other condenser andbearing against a part of said other condenser, whereby rotation of saidscrew operates to move one condenser relatively to the other and to movethe plates of both condensers to simultaneously increase or decrease thecapacitance of both condensers.

8. A single wide-range trimmer condenser comprising two trimmercondensers coupled together and arranged one above the other, each ofsaid trimmer condensers having its own insulation base with a set ofcondenser plates attached thereto, each said set consisting of a fiatbottom plate adjacent the base, a curved intermediate plate, aresilient-normally open top plate, and insulation films between saidplates, means connecting said trimmer condensers in parallel, one ofsaid condenser bases having a threaded part, and a single adjustingscrew mating with said threaded part and passing through the condenserplates of both condensers and through the base of the other condenserand bearing against a part of said other condenser, whereby rotation ofsaid screw operates to move one condenser relatively to the other and tomove the plates of both condensers to simultaneously increase ordecrease the capacitance of both condensers.

9. A single wide-range trimmer condenser comprising two trimmercondensers coupled together and arranged one above th other in face toface or inverted relation, each of said trimmer condensers comprising aninsulation base with a set of normally openable condenser platesattached thereto, means connecting said trimmer condensers in parallel,one of said condenser bases having a threaded part, and a singleadjusting screw mating with said threaded part and passingthrough thecondenser plates of both condensers and through the base of the othercondenser and bearing against said other base, whereby rotation of saidscrew operates to move one condenser relatively to the other and to movethe plates of both condensers to simultaneously increase or decrease thecapacitance of both condensers.

10'. A single wide-range trimmer condenser comprising two trimmercondensers coupled together and arranged one above the other in face toface or inverted relation, each of said trimmer condensers comprising aninsulation base with a set of normally cpenable condenser platesattached thereto, means connecting said trimmer condensers in parallel,one of said condenser bases having a threaded part, and a singleadjusting screw mating with said threaded part and passing through thecondenser plates of both condensers and through the base of the othercondenser and bearing against said other base, whereby rotation of saidscrew simultaneously adjusts both condensers and moves one condenserrelatively to the other, thereby providing a con denser of relativelylarge capacitance and high ratio of maximum-to-minimum capacitance.

JOSEPH A. FLANZER. PHILIP BEIN.

